C# .Net Bubble Sort Program Application

public partial class Form1 : Form
    {
        int[] a = new int[4];
        int result;
        int temp, max;
        public Form1()
        {
            InitializeComponent();
            groupBox2.Visible = false;
            this.MaximizeBox = false;
            this.MinimizeBox = false;
        }

        private void operationbtn_Click(object sender, EventArgs e)
        {
           a[0]=Convert.ToInt16(inputtxt1.Text);
           a[1] = Convert.ToInt16(inputtxt2.Text);
           a[2] = Convert.ToInt16(inputtxt3.Text);
           a[3] = Convert.ToInt16(inputtxt4.Text);
            
            max=4;
             for (int u = 0; u < max; u++)
             {

                 for (int i = 0; i < max - 1; i++)   //Loop for the array for the sorting
                 {                                                    
                                                                          
                if (a[i] > a[i + 1])
                {
                    temp = a[i];
                    a[i] = a[i + 1];
                    a[i + 1] = temp;
                }
                }

            }
            groupBox2.Visible = true;
            Outputtxt1.Text = Convert.ToString(a[0]);
            Outputtxt2.Text = Convert.ToString(a[1]);
            Outputtxt3.Text = Convert.ToString(a[2]);
            Outputtxt4.Text = Convert.ToString(a[3]);
           
        }
}